System and process for water treatment

ABSTRACT

A method for removing contaminant from feedwater by forming a dispersion comprising bubbles of a treatment gas in a continuous phase comprising feedwater, wherein the bubbles have a mean diameter of less than about 5 μm and wherein the treatment gas is selected from the group consisting of air, oxygen, and chlorine. A method for removing contaminants from a feedwater by subjecting a fluid mixture comprising feedwater and a treatment gas to a shear rate greater than 20,000 s −1  in a high shear device to produce a dispersion of treatment gas in a continuous phase of the feedwater. A system for treating feedwater to remove contaminants therefrom is also presented, the system comprising at least one high shear mixing device comprising at least one generator comprising a rotor and a stator separated by a shear gap; and a pump configured for delivering feedwater and treatment gas to the high shear mixing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C.§120 of U.S. patentapplication Ser. No. 12/142,447 filed Jun. 19, 2008 which claims thebenefit under 35 U.S.C.§119(e) of U.S. Provisional Application No.60/946,462 filed Jun. 27, 2007, the disclosures of both of which arehereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to water treatment. Moreparticularly, the present invention relates to a high shear system andprocess for water treatment. The disclosed system and method may be usedto treat waste or raw water containing contaminants whereby the watermay be disinfected, stabilized and/or contaminant(s) separated from thewater.

2. Background of the Invention

Processes for the recovery of waste water from industrial operationspresent challenging environmental issues and the government regulatesthese processes. The impact on the environment of waste water used inindustrial operations has led to governmental regulations at both thelocal and federal level. These regulations mandate cleanup of industrialwaste water prior to release to the environment and/or introduction intopublic sewer systems.

Several challenges to cleanup are presented by industrial andresidential waste waters. For example, the waste water often comprisessignificant amounts of suspended solids, undesirable dissolved minerals,and noxious gases. The waste water may also comprise significant amountsof organic materials, including hydrocarbons (e.g., oils) and bacteria.

Furthermore, raw water from surface sources (e.g. springs) orgroundwater sources often require treatment for contaminant removalprior to use, e.g. prior to use as drinking water.

Numerous water treatment schemes exist. For example, chemical oxidationprocesses are routinely used to remove organic contaminants from wastewater. Physical waste water treatment systems, including solid particleflocculation/flotation, are also common. However, there remains a needin the industry for improved systems and processes for treating wastewater whereby increased throughput, increased contaminant removal,and/or the use of reduced amounts of treatment aid (e.g. gases such aschlorine and air or liquids such as flocculants) are permitted.

SUMMARY

A high shear system and a high shear process for enhancing watertreatment are disclosed. The high shear system and process may reducemass transfer limitations relative to conventional water treatmentsystems and processes, thereby increasing the water treatment rate andpotentially permitting a reduction in contact time, an increasedremoval/neutralization of undesirable contaminants, and/or a reductionin treatment aid. The system and process employ an external high shearmechanical device to provide enhanced contact between reactants. In someembodiments, this enhanced contact results in accelerated chemicalreactions between multiphase reactants. In an embodiment, the processcomprises the use of an external pressurized high shear device toprovide for water treatment without the need for large volume vessels inwhich the water spends high residence times.

Herein disclosed is a method for removing contaminants from feedwater,the method comprising forming a dispersion comprising bubbles of atreatment gas in a continuous phase comprising feedwater, wherein thebubbles have a mean diameter of less than about 5 μm and wherein thetreatment gas is a gas selected from air, oxygen, and chlorine. Thefeedwater may be selected from the group consisting of waste water,surface water, groundwater, and combinations thereof. The contaminantmay be selected from hydrogen sulfide, hydrocarbons, particulate matter,bacteria, and volatile components. The gas bubbles may have a meandiameter of less than 1 μm, or no more than 400 nm. Forming thedispersion may comprise subjecting a mixture of the treatment gas andthe continuous phase to a shear rate of greater than about 20,000 s⁻¹.Forming the dispersion may comprise contacting the treatment gas and thecontinuous phase in a high shear device, wherein the high shear devicecomprises at least one rotor, and wherein the at least one rotor isrotated at a tip speed of at least 22.9 m/s (4,500 ft/min) duringformation of the dispersion. In embodiments, the high shear deviceproduces a local pressure of at least about 1034.2 MPa (150,000 psi) atthe tip of the at least one rotor during formation of the dispersion.The energy expenditure of the high shear device during formation of thedispersion may be greater than 1000 W/m³ of fluid. The method mayfurther comprise introducing the dispersion into a vessel and extractingparticle-containing water from the vessel. In embodiments, the methodfurther comprises introducing at least a portion of theparticle-containing water into a separator. At least a portion of theparticle-containing water may be recycled and additional dispersionformed therefrom.

Also disclosed is a method for removing contaminants from a feedwater,the method comprising subjecting a fluid mixture comprising treatmentgas and the feedwater to a shear rate greater than 20,000 s⁻¹ in a highshear device to produce a dispersion of treatment gas in a continuousphase of the feedwater, wherein the treatment gas is selected from thegroup consisting of air, oxygen, and chlorine. The method may furthercomprise introducing the dispersion into a vessel from which an aqueousproduct is removed and separating particles from the aqueous product.The contaminants may comprise dissolved organic matter, the treatmentgas may comprise air, oxygen, or both, the vessel may be an aerationvessel comprising micro-organisms that consume organic matter, and theparticles separated from the aqueous product may comprisemicro-organisms. At least a portion of the particles may be recycled tothe aeration vessel. In embodiments, the treatment gas compriseschlorine. The dispersion may be stable for at least about 15 minutes atatmospheric pressure.

Also disclosed herein is a system for treating feedwater to removecontaminants therefrom, the system comprising at least one high shearmixing device comprising at least one rotor and at least one statorseparated by a shear gap, wherein the shear gap is the minimum distancebetween the at least one rotor and the at least stator, and wherein thehigh shear mixing device is capable of producing a tip speed of the atleast one rotor of greater than 22.9 m/s (4,500 ft/min), and a pumpconfigured for delivering feedwater and treatment gas selected from thegroup consisting of oxygen, air, and chlorine to the high shear mixingdevice. The system may further comprise a tank from which treated wateris extracted, an inlet of the tank fluidly connected to the outlet ofthe external high shear device. In embodiments, the at least one highshear mixing device is capable of producing a tip speed at a tip of theat least one rotor of at least 40.1 m/s (7,900 ft/min). The system maycomprise at least two high shear mixing devices. The high shear devicemay comprise at least two generators. The shear rate provided by onegenerator may be greater than the shear rate provided by anothergenerator.

Certain embodiments of an above-described method or system potentiallyprovide for more optimal time, temperature and pressure conditions thanare otherwise possible, and which potentially increase the rate of thewater treatment process. Certain embodiments of the above-describedmethods or systems potentially provide overall cost reduction byoperating with reduced residence times, providing increased product perunit of treatment aid consumed, and/or reduced capital and/or operatingcosts. These and other embodiments and potential advantages will beapparent in the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred embodiment of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

FIG. 1 is a process flow diagram of a water treatment system accordingto an embodiment of the present disclosure.

FIG. 2 is a longitudinal cross-section view of a multi-stage high sheardevice, as employed in an embodiment of the system.

NOTATION AND NOMENCLATURE

As used herein, the term “dispersion” refers to a liquefied mixture thatcontains at least two distinguishable substances (or “phases”) that willnot readily mix and dissolve together. As used herein, a “dispersion”comprises a “continuous” phase (or “matrix”), which holds thereindiscontinuous droplets, bubbles, and/or particles of the other phase orsubstance. The term dispersion may thus refer to foams comprising gasbubbles suspended in a liquid continuous phase, emulsions in whichdroplets of a first liquid are dispersed throughout a continuous phasecomprising a second liquid with which the first liquid is immiscible,and continuous liquid phases throughout which solid particles aredistributed. As used herein, the term “dispersion” encompassescontinuous liquid phases throughout which gas bubbles are distributed,continuous liquid phases throughout which solid particles (e.g., solidcatalyst or contaminant) are distributed, continuous phases of a firstliquid throughout which droplets of a second liquid that issubstantially insoluble in the continuous phase are distributed, andliquid phases throughout which any one or a combination of solidparticles, immiscible liquid droplets, and gas bubbles are distributed.Hence, a dispersion can exist as a homogeneous mixture in some cases(e.g., liquid/liquid phase), or as a heterogeneous mixture (e.g.,gas/liquid, solid/liquid, or gas/solid/liquid), depending on the natureof the materials selected for combination. The term emulsion will beused herein more specifically to refer to liquid/liquid orliquid/liquid/solid dispersions.

The term “treatment aid” will be used to refer to any component added toa contaminated water stream. For example, in embodiments, a “treatmentaid” may comprise a treatment gas such as air, oxygen, or chlorine gas.In other embodiments, “treatment aid” may comprise a liquid such as aliquid flocculating agent.

DETAILED DESCRIPTION

Overview. The rate of chemical reactions involving liquids, gases andsolids depends on time of contact, temperature, and pressure. In caseswhere it is desirable to react two or more raw materials of differentphases (e.g. solid and liquid; liquid and gas; solid, liquid and gas),one of the limiting factors controlling the rate of reaction involvesthe contact time of the reactants. In the case of heterogeneouslycatalyzed reactions there is the additional rate limiting factor ofhaving the reacted products removed from the surface of the catalyst topermit the catalyst to catalyze further reactants. Contact time for thereactants and/or catalyst is often controlled by mixing which providescontact with two or more reactants involved in a chemical reaction. Inthe case of homogeneous reactions, for example liquid/liquid reactions,enhanced mixing may increase the rate or extent of interaction and alsohomogenize the temperature within the reaction zone(s).

A system and process for water treatment comprises an external highshear mechanical device to provide rapid contact and mixing of chemicalingredients in a controlled environment in the reactor/mixer device. Thedisclosed high shear system and method may be incorporated intoconventional water treatment processes, thereby enhancing removal orneutralization of contaminant (e.g., hydrocarbon, bacteria, noxious gas,etc.) and/or aeration rate. The high shear device may be used variouswater treatment processes, such as biological treatment processes thatremove dissolved organic material from the water, physical separationprocesses, and chemical treatment processes. The use of high shear mayreduce mass transfer limitations on the desired reactions/interactionsand thus reduce the time required for water treatment, therebyincreasing obtainable throughput. Product yield may be increased as aresult of the high shear system and process. The use of high shearcontacting of treatment aid and water to be treated may allow for theuse of decreased amounts of gas (e.g. air, chlorine) and/or liquid (e.g.liquid flocculating agents) treatment aids than conventional watertreatment processes.

The high shear system may be used to form a dispersion of a treatmentgas in a liquid, for example, a dispersion of oxygen, air, or chlorinein the water to be treated. Such a dispersion may enhance the amount ofdissolved gas due to the reduced diameter of the bubbles in thedispersion, which typically have a mean bubble diameter of less thanabout 5 μm. Although not discussed in detail herein, the high shearsystem may also be used to intimately mix two liquid streams, forexample, a water stream to be treated and a liquid flocculating agent.In these embodiments, the high shear device may increase theflocculation of contaminants by effecting intimate mixing withininteraction zone(s).

Other uses of the disclosed system and method will become apparent uponreading the disclosure and viewing the accompanying drawings. While thefollowing description will be given with respect to wastewater treatmentprocesses comprising chlorination and aeration, the embodimentsdescribed herein are exemplary only, and are not intended to belimiting. For example, the high shear system and process may be used forthe treatment of waste water or raw water and may be used for enhancingchlorination and aeration singularly, or any combination of gas and/orliquid injection known to those of skill in the art to be used in thetreatment of water streams.

Water Treatment System. A high shear water treatment system will now bedescribed in relation to FIG. 1, which is a process flow diagram of anembodiment of a high shear water treatment system 1 for treatment ofwater comprising at least one contaminant to be at least partiallyremoved, stabilized, and/or neutralized. Such a system 1 may be used foraeration in a biological or biochemical waste water treatment systemaccording to the activated sludge system or aeration in an aerobicaeration pond/lagoon. In embodiments, high shear system 1 is used togenerate air bubbles in a physical waste water treatment system (e.g.solid particle flotation system). The high shear system and process mayalso be utilized for the bactericidal treatment of water with, forexample chlorine gas.

It is widely known that chlorine can be effectively used to killbacteria contained in water. Chlorine is commonly used for treatingdrinking water, and also for treating water used in swimming poolsystems, and it is has been extensively used to treat waste water duringsewage treatment processes. While the addition of chlorine to water hasbeen found to be an effective method of killing bacteria contained inthe water, it has a number of disadvantages. Firstly, chlorine, which isa relatively volatile gas in its natural state, is rapidly dissipatedfrom water when left to stand open to the atmosphere, particularly whenthe water has a temperature of greater than about 70° F. It is thusgenerally necessary to make frequent additions of chlorine to waterunder these conditions in order to maintain the bacteria levels in thewater within safe ranges. This may be economically undesirable. Asdiscussed further below, the high shear system and process may permit areduction in the amount of chlorine needed for water treatment and/orincrease the rate of water treatment by minimizing resistance to masstransfer via high shear mixing and creation of a dispersion ofdisinfectant gas in a continuous aqueous phase.

The basic components of a representative high shear system include anexternal high shear mixing device (HSD), a vessel, and a pump. Each ofthese components is further described in more detail below. As shown inFIG. 1, high shear device 40 is located external to vessel/reactor 10.Line 21 is connected to pump 5 for introducing water to be treated. Line13 connects pump 5 to HSD 40, and line 18 connects HSD 40 to vessel 10.Line 22 may be connected to line 13 for introducing a treatment gas(e.g., air, oxygen, or chlorine) or liquid treatment aid. Alternatively,line 22 may be connected to an inlet of HSD 40. Line 17 may be connectedto vessel 10 for removal of unreacted treatment gas, hydrogen sulfide orother gas removed from the water by the treatment. Additional componentsor process steps may be incorporated between vessel 10 and HSD 40, orahead of pump 5 or HSD 40, if desired, as will become apparent uponreading the description of the high shear water treatment processdescribed hereinbelow.

High shear system 1 may further comprise preliminary treatmentapparatus, such as unit 60 which may be used to remove large solids andgreases from the water to be treated in line 25. Pretreatment unit 60may be connected to pump 5 via line 21. High shear system 1 may furthercomprise a separator 30 downstream of HSD 40 for separation ofsolids-heavy and solids-reduced products. Separator 30 may be connectedvia line 16 to vessel 10. Line 33 or line 36 from separator 30 may beconnected to line 21 or line 13 to provide for multi-pass operation, ifdesired. Inlet lines may be incorporated into high shear system 1 forintroducing material into the system. For example, line 14 may beconnected to vessel 10 for the introduction of material, such as pHadjustment aid, into vessel 10; and line 35 may be connected to line 16or elsewhere in high shear system 1 to introduce material, such asflocculant into high shear system 1. It should be noted that FIG. 1 is asimplified process diagram and potential pieces of process equipment,such as separators, valves, and compressors, have been omitted forclarity.

Pretreatment Unit(s). High shear system 1 may comprise pretreatmentunit(s) 60 for physical separation of components from the water to betreated. Pretreatment unit 60 may be configured to separate large solidobjects and/or grease from the water stream in line 25. Withoutlimitation, examples of suitable pretreatment apparatus are bar screens,grit tanks, and settling tanks.

High Shear Mixing Device. External high shear mixing device (HSD) 40,also sometimes referred to as a high shear device or high shear mixingdevice, is configured for receiving an inlet stream, via line 13,comprising water to be treated and treatment aid. Alternatively, HSD 40may be configured for receiving water and treatment aid via separateinlet lines (not shown). Although one high shear device 40 is shown inFIG. 1, it should be understood that some embodiments of the system mayhave one or more than two high shear mixing devices arranged either inseries or parallel flow. HSD 40 is a mechanical device that utilizes oneor more generators comprising a rotor/stator combination, each of whichhas a gap between the stator and rotor. The gap between the rotor andthe stator in each generator set may be fixed or may be adjustable. HSD40 is configured in such a way that it is capable of producing submicronand micron-sized bubbles or droplets of treatment aid in an aqueousmixture flowing through the high shear device. The high shear devicecomprises an enclosure or housing so that the pressure and temperatureof the aqueous mixture may be controlled.

High shear mixing devices are generally divided into three generalclasses, based upon their ability to mix fluids. Mixing is the processof reducing the size of particles or inhomogeneous species within thefluid. One metric for the degree or thoroughness of mixing is the energydensity per unit volume that the mixing device generates to disrupt thefluid particles. The classes are distinguished based on delivered energydensities. Three classes of industrial mixers having sufficient energydensity to consistently produce mixtures or emulsions with particlesizes in the range of submicron to 50 microns include homogenizationvalve systems, colloid mills and high speed mixers. In the first classof high energy devices, referred to as homogenization valve systems,fluid to be processed is pumped under very high pressure through anarrow-gap valve into a lower pressure environment. The pressuregradients across the valve and the resulting turbulence and cavitationact to break-up any particles in the fluid. These valve systems are mostcommonly used in milk homogenization and can yield average particlesizes in the submicron to about 1 micron range.

At the opposite end of the energy density spectrum is the third class ofdevices referred to as low energy devices. These systems usually havepaddles or fluid rotors that turn at high speed in a reservoir of fluidto be processed, which in many of the more common applications is a foodproduct. These low energy systems are customarily used when averageparticle sizes of greater than 20 microns are acceptable in theprocessed fluid.

Between the low energy devices and homogenization valve systems, interms of the mixing energy density delivered to the fluid, are colloidmills and other high speed rotor-stator devices, which are classified asintermediate energy devices. A typical colloid mill configurationincludes a conical or disk rotor that is separated from a complementary,liquid-cooled stator by a closely-controlled rotor-stator gap, which iscommonly between 0.02 mm to 10 mm (0.001-0.40 inch). Rotors are usuallydriven by an electric motor through a direct drive or belt mechanism. Asthe rotor rotates at high rates, it pumps fluid between the rotor andthe stator, and shear forces generated in the gap process the fluid.Many colloid mills with proper adjustment achieve average particle sizesof 0.1-25 microns in the processed fluid. These capabilities rendercolloid mills appropriate for a variety of applications includingcolloid and oil/water-based emulsion processing such as that requiredfor cosmetics, mayonnaise, or silicone/silver amalgam formation, toroofing-tar mixing.

Tip speed is the circumferential distance traveled by the tip of therotor per unit of time. Tip speed is thus a function of the rotordiameter and the rotational frequency. Tip speed (in meters per minute,for example) may be calculated by multiplying the circumferentialdistance transcribed by the rotor tip, 2πR, where R is the radius of therotor (meters, for example) times the frequency of revolution (forexample revolutions per minute, rpm). A colloid mill, for example, mayhave a tip speed in excess of 22.9 m/s (4500 ft/min) and may exceed 40m/s (7900 ft/min). For the purpose of this disclosure, the term ‘highshear’ refers to mechanical rotor stator devices (e.g., colloid mills orrotor-stator dispersers) that are capable of tip speeds in excess of 5.1m/s. (1000 ft/min) and require an external mechanically driven powerdevice to drive energy into the stream of products to be reacted. Forexample, in HSD 40, a tip speed in excess of 22.9 m/s (4500 ft/min) isachievable, and may exceed 40 m/s (7900 ft/min). In some embodiments,HSD 40 is capable of delivering at least 300 L/h at a tip speed of atleast 22.9 m/s (4500 ft/min). The power consumption may be about 1.5 kW.HSD 40 combines high tip speed with a very small shear gap to producesignificant shear on the material being processed. The amount of shearwill be dependent on the viscosity of the fluid. Accordingly, a localregion of elevated pressure and temperature is created at the tip of therotor during operation of the high shear device. In some cases thelocally elevated pressure is about 1034.2 MPa (150,000 psi). In somecases the locally elevated temperature is about 500° C. In some cases,these local pressure and temperature elevations may persist for nano orpico seconds.

An approximation of energy input into the fluid (kW/L/min) can beestimated by measuring the motor energy (kW) and fluid output (L/min).As mentioned above, tip speed is the velocity (ft/min or m/s) associatedwith the end of the one or more revolving elements that is creating themechanical force applied to the fluid. In embodiments, the energyexpenditure of HSD 40 is greater than 1000 W/m³. In embodiments, theenergy expenditure of HSD 40 is in the range of from about 3000 W/m³ toabout 7500 W/m³.

The shear rate is the tip speed divided by the shear gap width (minimalclearance between the rotor and stator). The shear rate generated in HSD40 may be in the greater than 20,000 s⁻¹. In some embodiments the shearrate is at least 40,000 s⁻¹. In some embodiments the shear rate is atleast 100,000 s⁻¹. In some embodiments the shear rate is at least500,000 s⁻¹. In some embodiments the shear rate is at least 1,000,000s⁻¹. In some embodiments the shear rate is at least 1,600,000 s⁻¹. Inembodiments, the shear rate generated by HSD 40 is in the range of from20,000 s⁻¹ to 100,000 s⁻¹. For example, in one application the rotor tipspeed is about 40 m/s (7900 ft/min) and the shear gap width is 0.025 mm(0.001 inch), producing a shear rate of 1,600,000 s⁻¹. In anotherapplication the rotor tip speed is about 22.9 m/s (4500 ft/min) and theshear gap width is 0.0254 mm (0.001 inch), producing a shear rate ofabout 901,600 s⁻¹.

HSD 40 is capable of highly dispersing or transporting treatment aidinto a main liquid phase (continuous phase) comprising water, with whichit would normally be immiscible, at conditions such that at least aportion of the treatment aid reacts/interacts with contaminant in thewater. In some embodiments, HSD 40 comprises a colloid mill. Suitablecolloidal mills are manufactured by IKA® Works, Inc. Wilmington, N.C.and APV North America, Inc. Wilmington, Mass., for example. In someinstances, HSD 40 comprises the DISPAX REACTOR® of IKA® Works, Inc.

The high shear device comprises at least one revolving element thatcreates the mechanical force applied to the aqueous mixture. The highshear device comprises at least one stator and at least one rotorseparated by a clearance. For example, the rotors may be conical or diskshaped and may be separated from a complementarily-shaped stator. Inembodiments, both the rotor and stator comprise a plurality ofcircumferentially-spaced teeth. In some embodiments, the stator(s) areadjustable to obtain the desired shear gap between the rotor and thestator of each generator (rotor/stator set). Grooves between the teethof the rotor and/or stator may alternate direction in alternate stagesfor increased turbulence. Each generator may be driven by any suitabledrive system configured for providing the necessary rotation.

In some embodiments, the minimum clearance (shear gap width) between thestator and the rotor is in the range of from about 0.0254 mm (0.001inch) to about 3.175 mm (0.125 inch). In certain embodiments, theminimum clearance (shear gap width) between the stator and rotor isabout 1.5 mm (0.060 inch). In certain configurations, the minimumclearance (shear gap) between the rotor and stator is at least 1.7 mm(0.07 inch). The shear rate produced by the high shear device may varywith longitudinal position along the flow pathway. In some embodiments,the rotor is set to rotate at a speed commensurate with the diameter ofthe rotor and the desired tip speed. In some embodiments, the high sheardevice has a fixed clearance (shear gap width) between the stator androtor. Alternatively, the high shear device has adjustable clearance(shear gap width).

In some embodiments, HSD 40 comprises a single stage dispersing chamber(i.e., a single rotor/stator combination, a single generator). In someembodiments, high shear device 40 is a multiple stage inline disperserand comprises a plurality of generators. In certain embodiments, HSD 40comprises at least two generators. In other embodiments, high sheardevice 40 comprises at least 3 high shear generators. In someembodiments, high shear device 40 is a multistage mixer whereby theshear rate (which, as mentioned above, varies proportionately with tipspeed and inversely with rotor/stator gap width) varies withlongitudinal position along the flow pathway, as further describedherein below.

In some embodiments, each stage of the external high shear device hasinterchangeable mixing tools, offering flexibility. For example, the DR2000/4 DISPAX REACTOR® of IKA® Works, Inc. Wilmington, N.C. and APVNorth America, Inc. Wilmington, Mass., comprises a three stagedispersing module. This module may comprise up to three rotor/statorcombinations (generators), with choice of fine, medium, coarse, andsuper-fine for each stage. This allows for creation of dispersionshaving a narrow distribution of the desired bubble (e.g., treatment gasbubbles). In some embodiments, each of the stages is operated withsuper-fine generator. In some embodiments, at least one of the generatorsets has a rotor/stator minimum clearance (shear gap width) of greaterthan about 5 mm (0.2 inch). In alternative embodiments, at least one ofthe generator sets has a minimum rotor/stator clearance of greater thanabout 1.7 mm (0.07 inch).

Referring now to FIG. 2, there is presented a longitudinal cross-sectionof a suitable high shear device 200. High shear device 200 of FIG. 2 isa dispersing device comprising three stages or rotor-statorcombinations. High shear device 200 is a dispersing device comprisingthree stages or rotor-stator combinations, 220, 230, and 240. Therotor-stator combinations may be known as generators 220, 230, 240 orstages without limitation. Three rotor/stator sets or generators 220,230, and 240 are aligned in series along drive shaft 250.

First generator 220 comprises rotor 222 and stator 227. Second generator230 comprises rotor 223, and stator 228. Third generator 240 comprisesrotor 224 and stator 229. For each generator the rotor is rotatablydriven by input 250 and rotates about axis 260 as indicated by arrow265. The direction of rotation may be opposite that shown by arrow 265(e.g., clockwise or counterclockwise about axis of rotation 260).Stators 227, 228, and 229 may be fixably coupled to the wall 255 of highshear device 200.

As mentioned hereinabove, each generator has a shear gap width which isthe minimum distance between the rotor and the stator. In the embodimentof FIG. 2, first generator 220 comprises a first shear gap 225; secondgenerator 230 comprises a second shear gap 235; and third generator 240comprises a third shear gap 245. In embodiments, shear gaps 225, 235,245 have widths in the range of from about 0.025 mm to about 10 mm.Alternatively, the process comprises utilization of a high shear device200 wherein the gaps 225, 235, 245 have a width in the range of fromabout 0.5 mm to about 2.5 mm. In certain instances the shear gap widthis maintained at about 1.5 mm. Alternatively, the width of shear gaps225, 235, 245 are different for generators 220, 230, 240. In certaininstances, the width of shear gap 225 of first generator 220 is greaterthan the width of shear gap 235 of second generator 230, which is inturn greater than the width of shear gap 245 of third generator 240. Asmentioned above, the generators of each stage may be interchangeable,offering flexibility. High shear device 200 may be configured so thatthe shear rate will increase stepwise longitudinally along the directionof the flow 260.

Generators 220, 230, and 240 may comprise a coarse, medium, fine, andsuper-fine characterization. Rotors 222, 223, and 224 and stators 227,228, and 229 may be toothed designs. Each generator may comprise two ormore sets of rotor-stator teeth. In embodiments, rotors 222, 223, and224 comprise more than 10 rotor teeth circumferentially spaced about thecircumference of each rotor. In embodiments, stators 227, 228, and 229comprise more than ten stator teeth circumferentially spaced about thecircumference of each stator. In embodiments, the inner diameter of therotor is about 12 cm. In embodiments, the diameter of the rotor is about6 cm. In embodiments, the outer diameter of the stator is about 15 cm.In embodiments, the diameter of the stator is about 6.4 cm. In someembodiments the rotors are 60 mm and the stators are 64 mm in diameter,providing a clearance of about 4 mm. In certain embodiments, each ofthree stages is operated with a super-fine generator, comprising a sheargap of between about 0.025 mm and about 4 mm. For applications in whichsolid particles are to be sent through high shear device 40, theappropriate shear gap width (minimum clearance between rotor and stator)may be selected for an appropriate reduction in particle size andincrease in particle surface area. In embodiments, this may bebeneficial for increasing the flotation of solid particles.

High shear device 200 is configured for receiving from line 13 a mixtureat inlet 205. The mixture comprises treatment aid as the dispersiblephase and water to be treated as the continuous phase. The feed streamwill typically further comprise a particulate solid (e.g. contaminant)component. Feed stream entering inlet 205 is pumped serially throughgenerators 220, 230, and then 240, such that product dispersion isformed. Product dispersion exits high shear device 200 via outlet 210(and line 18 of FIG. 1). The rotors 222, 223, 224 of each generatorrotate at high speed relative to the fixed stators 227, 228, 229,providing a high shear rate. The rotation of the rotors pumps fluid,such as the feed stream entering inlet 205, outwardly through the sheargaps (and, if present, through the spaces between the rotor teeth andthe spaces between the stator teeth), creating a localized high shearcondition. High shear forces exerted on fluid in shear gaps 225, 235,and 245 (and, when present, in the gaps between the rotor teeth and thestator teeth) through which fluid flows process the fluid and createproduct dispersion. Product dispersion exits high shear device 200 viahigh shear outlet 210 (and line 18 of FIG. 1).

The product dispersion has an average gas bubble, droplet or particlesize of less than about 5 μm. In embodiments, HSD 40 produces adispersion having a mean bubble, droplet and/or particle size of lessthan about 1.5 μm. In embodiments, HSD 40 produces a dispersion having amean bubble, droplet and/or particle size of less than 1 μm; preferablythe bubbles, droplets or particles of treatment aid are sub-micron indiameter. In certain instances, the average bubble, droplet or particlesize is from about 0.1 μm to about 1.0 μm. In embodiments, HSD 40produces a dispersion having a mean bubble, droplet or particle size ofless than 400 nm. In embodiments, HSD 40 produces a dispersion having amean bubble, droplet or particle size of less than 100 nm. High sheardevice 40 produces a dispersion comprising droplets, particles and/orgas bubbles capable of remaining dispersed at atmospheric pressure forat least about 15 minutes.

Not to be limited by theory, it is known in emulsion chemistry thatsub-micron particles, or bubbles, dispersed in a liquid undergo movementprimarily through Brownian motion effects. The bubbles in the productdispersion created by high shear device 200 may have greater mobilitythrough boundary layers of solid contaminant particles, therebyfacilitating and accelerating the reaction/interaction through enhancedtransport of reactants.

In certain instances, high shear device 200 comprises a DISPAX REACTOR®of IKA® Works, Inc. Wilmington, N.C. and APV North America, Inc.Wilmington, Mass. Several models are available having variousinlet/outlet connections, horsepower, tip speeds, output rpm, and flowrate. Selection of the high shear device will depend on throughputrequirements and desired particle, droplet or bubble size in dispersionin line 18 (FIG. 1) exiting outlet 210 of high shear device 200. IKA®model DR 2000/4, for example, comprises a belt drive, 4M generator, PTFEsealing ring, inlet flange 25.4 mm (1 inch) sanitary clamp, outletflange 19 mm (¾ inch) sanitary clamp, 2HP power, output speed of 7900rpm, flow capacity (water) approximately 300-700 L/h (depending ongenerator), a tip speed of from 9.4-41 m/s (1850 ft/min to 8070 ft/min).

Vessel. Vessel or reactor 10 is any type of vessel in which watertreatment can propagate. For instance, a continuous or semi-continuousstirred tank reactor, or one or more batch reactors may be employed inseries or in parallel. In some applications vessel 10 may be a clarifieror other type of separator. In embodiments, vessel 10 is an aerationtank. Any number of reactor inlet lines is envisioned, with two shown inFIG. 1 (lines 14 and 18). Inlet line 14 may be an alkaline inlet lineconnected to vessel 10 for introducing pH adjustment aid duringoperation of the system. Vessel 10 may comprise an exit line 17 for ventgas, and an outlet product line 16 for an aqueous stream. Inembodiments, vessel 10 comprises a plurality of reactor product lines16; for example, if vessel 10 is a separator, the vessel may comprise anoutlet for solids and an outlet for clarified water.

Treatment (e.g. aeration or chlorination) will occur whenever suitabletime, temperature and pressure conditions exist. In this senseinteraction of contaminant and treatment aid, for example chemicaloxidation, can occur at any point in the flow diagram of FIG. 1 ifcontact is suitable. In embodiments, significant reaction (e.g.chlorination) may occur within HSD 40 and a discrete vessel 10 may beunnecessary. That is, in some applications vessel 10 may be omitted. Forexample, if multiple high shear devices/reactors are employed in seriesor if HSD 40 is used to aerate water prior to introduction into anaerated lagoon, as further described below, vessel 10 may be absent. Insuch instances, product from HSD 40 may be introduced directly into aseparator 30 or an aerated lagoon or pond. The size of reactor 10 mayvary considerably, depending upon the equipment and the amount of wastematerial to be processed therein.

Vessel 10 may include one or more of the following components: stirringsystem, heating and/or cooling capabilities, pressure measurementinstrumentation, temperature measurement instrumentation, one or moreinjection points, and level regulator (not shown), as are known in theart of reaction vessel design. For example, a stirring system mayinclude a motor driven mixer. A heating and/or cooling apparatus maycomprise, for example, a heat exchanger.

Pumps. Pump 5 is configured for either continuous or semi-continuousoperation, and may be any suitable pumping device that is capable ofproviding controlled flow through HSD 40 and high shear system 1. Inembodiments, the system is operated at or near atmospheric pressure.Pump 5 may be configured to provide greater than 202.65 kPa (2 atm)pressure or greater than 303.975 kPa (3 atm) pressure. For example, aRoper Type 1 gear pump, Roper Pump Company (Commerce Georgia) DaytonPressure Booster Pump Model 2P372E, Dayton Electric Co (Niles, Ill.) isone suitable pump. Preferably, all contact parts of the pump comprisestainless steel, for example, 316 stainless steel. In some embodimentsof the system, pump 5 is capable of pressures greater than about 2026.5kPa (20 atm). In addition to pump 5, one or more additional pumps (notshown) may be included in the system illustrated in FIG. 1. For example,a booster pump, which may be similar to pump 5, may be included betweenHSD 40 and vessel 10 for boosting the pressure into vessel 10, or arecycle pump may be positioned on line 17 for recycling gas from vessel10 to HSD 40. As another example, a supplemental feed pump, which may besimilar to pump 5, may be included for introducing additional materialinto vessel 10.

Separator. Separator 30 is any suitable vessel which may be configuredto separate treated water from solid contaminant. Separator 30 may be,for example, a clarifier. In embodiments, treated water is removed frombelow floated solids in separator 30 via line 36, while, in otherembodiments, treated water is extracted via line 33 from above solidswhich have been allowed to settle to a lower portion of separator 30.

Water Treatment Process. Operation of high shear water treatment system1 will now be discussed with reference to aeration and chlorination.

Feedstream. Line 25 comprises water to be treated. Feedstream in line 25may be waste material, such as sewage or septic waste waters of a smallcommunity or of a factory. In embodiments, feedwater comprises wastematerial from other sources, such as a municipal treatment system, awaste discharge system from an industrial plant or food processinginstallation, etc. In embodiments, a portion of the water in high shearsystem inlet line 21 comprises water recycled via line 45 from separator30 or vessel 10. In embodiments, the water to be treated comprises rawwater, for example, surface water or underground water that may betreated with, for example, chlorination via the disclosed system andprocess for disinfection of the water prior to its use as drinkingwater. Such raw surface or underground water may comprise gas such asnaturally occurring hydrogen sulfide, gases produced via living organicmaterial such as algae, gases produced via degradation of organicmaterial, residual chlorine, and etc. The water may therefore beaerated, according to embodiments of the present disclosure, tofacilitate the release of these gases. Such removal of gases from rawwater may ameliorate taste and/or odor problems prior to use of thewater as drinking water. In embodiments, the water is aerated andintroduced into an aeration vessel 10 comprising microorganisms known toconsume oxygen and organic matter in the wastewater.

Pretreatment. In embodiments, waste water enters a pretreatment device60 via inlet line 25. For example, pretreatment device 60 may comprise abar screen, grit tank, settling tank, or filtration subsystem, as knownto those of skill in the art. Pretreatment device 60 may comprise, forexample, a bag filter. Pretreatment unit 60 may be configured to removegrease and/or large solids such as metal components from water in line25. Pretreatment discharge in line 26 comprises material that is not tobe incorporated in the water in line 21 that is processed in HSD 40.

Dispersion Formation. Line 21 introduces water to be treated into pump5. A dispersible gaseous treatment aid comprising air, oxygen, orchlorine or a dispersible liquid treatment aid is introduced into system1 via line 22, and combined in line 13 with the aqueous stream to betreated. In embodiments, dispersible gas in line 22 comprises oxygen. Inembodiments, dispersible gas in line 22 comprises chlorine. Inembodiments, dispersible gas in line 22 comprises air. In embodiments,line 22 comprises dispersible liquid treatment aid (e.g. flocculant).

In embodiments, the dispersible treatment aid is fed directly into HSD40, instead of being combined with the liquid feedwater stream in line13. Pump 5 may be operated to pump the liquid feedwater through line 21,may build pressure and feed HSD 40, and may provide a controlled flowthroughout high shear device (HSD) 40 and high shear system 1. In someembodiments, pump 5 increases the pressure of the HSD inlet stream togreater than 200 kPa (2 atm) or greater than about 300 kPa (3atmospheres). In this way, high shear system 1 may combine high shearwith pressure to enhance intimate mixing of water and treatment aid.

After pumping, the dispersible treatment aid and the feedwater to betreated are mixed within HSD 40, which serves to create a finedispersion (which may be, for example, a liquid/liquid emulsion or agas/liquid dispersion) of the treatment aid in the feedwater. Within HSD40, the treatment aid and the feedwater are highly dispersed such thatnanobubbles (nanodroplets), submicron-sized bubbles (droplets), and/ormicrobubbles (microdroplets) of the treatment aid are formed forsuperior dissolution into solution and mixing enhancement. For example,disperser IKA® model DR 2000/4, a high shear, three stage dispersingdevice configured with three rotors in combination with stators, alignedin series, may be used to create the dispersion of treatment aid inliquid medium comprising feedwater. The rotor/stator sets may beconfigured as illustrated in FIG. 2, for example. The combined reactantsenter the high shear device via line 13 and enter a first stagerotor/stator combination. The rotors and stators of the first stage mayhave circumferentially spaced first stage rotor teeth and stator teeth,respectively. The coarse dispersion exiting the first stage enters thesecond rotor/stator stage. The rotor and stator of the second stage mayalso comprise circumferentially spaced rotor teeth and stator teeth,respectively. The reduced bubble or droplet-size dispersion emergingfrom the second stage enters the third stage rotor/stator combination,which may comprise a rotor and a stator having rotor teeth and statorteeth, respectively. The dispersion exits the high shear device via line18. In some embodiments, the shear rate increases stepwiselongitudinally along the direction of the flow, 260. For example, insome embodiments, the shear rate in the first rotor/stator stage isgreater than the shear rate in subsequent stage(s). In otherembodiments, the shear rate is substantially constant along thedirection of the flow, with the shear rate in each stage beingsubstantially the same.

If HSD 40 includes a PTFE seal, the seal may be cooled using anysuitable technique that is known in the art. For example, the feedwaterstream flowing in line 13 or line 21 may be used to cool the seal and inso doing be preheated prior to entering high shear device 40.

The rotor(s) of HSD 40 may be set to rotate at a speed commensurate withthe diameter of the rotor and the desired tip speed. As described above,the high shear device (e.g., colloid mill or toothed rim disperser) haseither a fixed clearance between the stator and rotor or has adjustableclearance. HSD 40 serves to intimately mix the dispersible treatment aidand the feedwater. In some embodiments of the process, the transportresistance of the reactants is reduced by operation of the high sheardevice such that the velocity of reaction/interaction is increased bygreater than about 5%. In some embodiments of the process, the transportresistance of the reactants is reduced by operation of the high sheardevice such that the velocity of reaction/interaction is increased bygreater than a factor of about 5. In some embodiments, the velocity ofreaction/interaction is increased by at least a factor of 10. In someembodiments, the velocity is increased by a factor in the range of about10 to about 100 fold.

In some embodiments, HSD 40 delivers at least 300 L/h at a tip speed ofat least 4500 ft/min, and which may exceed 7900 ft/min (40 m/s). Thepower consumption may be about 1.5 kW. Although measurement ofinstantaneous temperature and pressure at the tip of a rotating shearunit or revolving element in HSD 40 is difficult, it is estimated thatthe localized temperature seen by the fluid therein is in excess of 500°C. and at pressures in excess of 500 kg/cm² under cavitation conditions.The high shear mixing results in dispersion of the dispersible treatmentaid in micron or submicron-sized bubbles or droplets. In someembodiments, the resultant dispersion has an average bubble or dropletsize less than about 1.5 μm. Accordingly, the dispersion exiting HSD 40via line 18 comprises micron and/or submicron-sized droplets or gasbubbles. In some embodiments, the mean bubble or droplet size is in therange of about 0.4 μm to about 1.5 μm. In some embodiments, theresultant dispersion has an average bubble or droplet size less than 1μm. In some embodiments, the mean bubble or droplet size is less thanabout 400 nm, and may be about 100 nm in some cases. In manyembodiments, the dispersion is able to remain dispersed at atmosphericpressure for at least 15 minutes.

Once dispersed, the resulting gas/liquid/solid or liquid/liquid/soliddispersion exits HSD 40 via line 18 and feeds into vessel 10, asillustrated in FIG. 1.

Aeration. In instances where high shear system 1 is used for aeration,dispersion in line 18 comprises oxygen or air dispersed in the water.The aeration may be used for physical wastewater treatment or biologicalwastewater treatment utilizing micro-organisms that consume oxygen.

In a waste water treatment system according to the activated sludgeprocess, a continuous culture of mixed microorganisms is maintained inthe presence of dissolved oxygen using organic substances contained inthe waste water as a culture medium. The organic substances are oxidizedand separated (e.g. by sedimentation) from a flock of microorganisms oran activated sludge which comprises the medium and mixed microorganisms.The aerobic aerated lagoon process operates based on a similarprinciple, but does not include feedback of activated sludge.

In the biochemical treatment of waste water, aeration effectsdissolution of oxygen contained in the air into the waste water and/ordissipation of unnecessary gas or volatile material contained in thewater. Aeration usually accompanies a mixing or agitation of the wastewater. The supply of oxygen enables biochemical reactions such as theoxidation of organic substances, growth of microorganisms orself-oxidation by the activated sludge to proceed while mixing andagitation permits a satisfactory suspension of the activated sludge forachieving an efficient contact between absorbed oxygen and the sludge.Aeration may occur within HSD 40 and a vessel 10 into which thedispersion of air/oxygen in wastewater flows and to which activatedsludge is fed back. In a lagoon process, aeration may continue in alagoon in which the waste water dwells for a relatively long period oftime. The rates of the biochemical reactions depend on the period ofaeration and the quantity of microorganisms and organic materials; suchreactions typically proceed at a slow rate as compared with otherchemical reactions. Accordingly, larger treatment vessels and anincreased space for installation are generally required. The use of highshear device 40 in such an aeration process may serve to increase therate and/or effectiveness of such aeration processes and may reducetreatment vessel volume requirements or quantities of treatment aidneeded for sufficient water treatment.

In embodiments, the high shear system is used to enhance aeration of awater stream. Biochemical Oxygen Demand or Biological Oxygen Demand(BOD) is a chemical procedure used to determine how fast biologicalorganisms use up oxygen in a body of water. BOD may be used to indicatethe effectiveness of wastewater treatment. In the high shear aerationprocess disclosed herein, the oxygen absorption relative to the quantityof oxygen injected, or the oxygen absorption efficiency, may be greatlyimproved. In embodiments, the BOD is increased utilizing high shear.Consequently, the aeration period required may be reduced, a morecompact aeration vessel 10 having a high volume duty designed, or, insome embodiments, a discrete vessel 10 eliminated.

In aeration processes, dispersion comprising air dispersed in acontinuous phase of the water to be treated may be introduced into anaeration vessel 10. In embodiments, vessel 10 comprises microorganisms.Alternatively, the dispersion in line 18 may be introduced directly intoa pond or lagoon in which microorganisms are present which consumedissolved organic material in the water. In embodiments, physicalwastewater treatment using aeration is performed, vessel 10 is absent,and the dispersion comprising oxygen dispersed in water is introduceddirectly into a separator 30, or an aeration lagoon or pond. Within anaeration lagoon or pond, solids may be allowed to settle from thetreated water which may be removed by pumping, evaporation or otherconventional water removal technique.

In embodiments utilizing a vessel 10, vessel/reactor 10 may be operatedin either continuous or semi-continuous flow mode, or it may be operatedin batch mode. The contents of vessel 10 may be maintained at aspecified reaction temperature using heating and/or cooling capabilities(e.g., cooling coils) and temperature measurement instrumentation.Pressure in the vessel may be monitored using suitable pressuremeasurement instrumentation, and the level of reactants in the vesselmay be controlled using a level regulator (not shown), employingtechniques that are known to those of skill in the art. The contents maybe stirred continuously or semi-continuously with a mechanical mixingapparatus, for example. Vessel 10 may be operated at or near roomtemperature and atmospheric pressure. Vessel 10 may comprisemicro-organisms. In such embodiments, the microorganisms consume atleast a portion of the dissolved organic matter in the water and consumetreatment gas (e.g. oxygen) in the process.

Product gas, such as hydrogen sulfide released in the aeration process,and unconsumed treatment gas may exit vessel 10 via gas line 17.Unreacted treatment gas may be removed from line 17 and recycled to HSD40 or vessel 10, if desired.

In the embodiment of FIG. 1, water exits vessel 10 by way of line 16. Inembodiments, product stream in line 16 comprises water and solids. Inembodiments in which vessel 10 comprises micro-organisms, the product inoutlet line 16 may further comprise micro-organisms. In embodiments,product in line 16 is introduced into separator 30. Separator 30 mayseparate treated water from solids. In embodiments, the solids areflocculated and treated water removed from the bottom portion ofseparator 30. In such embodiments, line 35 may introduce a flocculatingagent into line 16 to enhance the flotation of solids above the treatedwater in separator 30. The flocculating agent may be a conventionalflocculant which helps flocculate fine particles so that they morerapidly coalesce and float as a sludge upon the water. It is alsoenvisioned that a high shear device similar to HSD 40 may be used tointroduce a liquid (or solid) flocculant.

In other embodiments, product in line 16 is introduced into separator30, solids are allowed to settle to the bottom of the separator, andtreated water is removed via a line 33 from the top portion of separator30. In embodiments in which vessel 10 and product in line 16 comprisemicro-organisms, a portion of the microorganisms separated from thetreated water in separator 30 may be recycled to vessel 10 via line 36(if solids are sedimented within separator 30) or line 33 (if solids arefloated within separator 30) and recycle line 44 to repopulate themicro-organisms in vessel 10. Remaining solids separated from thetreated water may be sent to a solids handling system. Treated waterproduced by aeration as described may be further treated with chemicaloxidation as discussed below.

Chemical Oxidation. The high shear system 1 may be used in a chlorineoxidation waste water treatment method. Chemical oxidation may disinfector stabilize solid particles in the water and produce a substantiallywater-free sludge. In these applications, dispersible treatment aid inline 22 comprises chlorine gas for chemical oxidation of the wastewaterand the product dispersion in line 18 comprises chlorine dispersed in acontinuous aqueous phase. A portion of dispersible gas in line 22 maycomprise chlorine gas recycled from elsewhere in the system, forexample, removed from the gas exiting vessel 10 via gas line 17. Thedispersion may be introduced into vessel 10. As a result of the intimatemixing of the reactants prior to entering vessel 10, a significantportion of the chemical oxidation may take place in HSD 40.

Introduction of dispersible gas comprising chlorine into line 22 intothe water to be treated produces hypochlorous acid, which producesnascent oxygen and hypochlorite ions. Organic solid particles in thewater are oxidized and minute gas bubbles formed, including nitrogen andcarbon dioxide, which may adhere to the particles. The reaction betweenthe chlorine gas and the waste water materials produces hydrochloricacid and hypochlorous acid. In the desired (substantially neutral) rangeof pH, more hypochlorous acid may be formed by the gaseous chlorine thanhydrochloric acid. Although hydrochloric acid (HCl) will not oxidize thesolid organic particles, it will aid in disinfection. The hypochlorousacid (HOCl) as well as the hypochlorite ion, which is also formed by andwith the HOCl, are powerful oxidizers. The pH may be controlled suchthat a sufficient quantity of strong oxidants is present, particularlyhypochlorous acid, which is the most powerful oxidizer present.

The pH of the waste water may be altered via means known to those ofskill in the art. For example, subsequent to pretreatment 60, a holdingtank may be used to adjust the pH to a level which is close toacid-alkaline neutrality, that is, in the pH range of from about 6.5 toabout 7.5 or more preferably in the pH range of from about 6.8 to about7.0. Waste water is typically at a lower pH than this, and therefore,the addition of sodium hydroxide, lime or the like may be used in highshear system 1 to raise the pH to the desired level. Conversely, if thewaste material is too alkaline, the pH may be lowered by adding water ata lower pH or acid. In some embodiments, pH adjustment material is addedelsewhere to high shear system 1, for example via reactor inlet line 14or into line 13. A pH adjustment pretreatment of the raw materialintroduced via line 21 may permit formation of greater amounts of themore effective oxidants, particularly hypochlorous acid. This may aid instabilization of the waste solids.

Use of a substantially neutral pH level in a high shear system 1 maythus be desirable for elimination of offensive odors and result in ahigher degree of disinfection and/or stabilization of the resultingsludge. The use of high shear device 40 may permit more completeoxidation of the solid waste particles by enhancing contact of thecontaminants with oxidant. When the process is operated in theabove-mentioned desired pH range, sufficient hypochlorous acid may beformed to effectively disinfect the solid materials, that is, to destroythe pathogens (i.e., the bacteria and viruses, etc.) and to eliminatefurther bacterial growth.

In an embodiment, waste water material comprising particles of organicsolids suspended in water is treated by mixing the feedwater thoroughlywith chlorine gas in high shear device 40. Oxidizing reactions betweenthe chlorine and the water stabilize and/or disinfect the otherwiseputrescible, unstable solid waste particles. Chlorine gas may beintroduced into line 13 or directly into HSD 40. The amount of chlorineintroduced into high shear system 1 will vary depending upon the natureof the material being treated, the flow rate, etc. The chlorine dosagemay run from 700-3000 mg/L.

The dispersion in line 18 comprising chlorine dispersed in a continuousphase of the water to be treated may be introduced into vessel 10.Within vessel 10, chemical oxidation reactions continue. Vessel/reactor10 may be operated in either continuous or semi-continuous flow mode, orit may be operated in batch mode. The contents of vessel 10 may bemaintained at a specified reaction temperature using heating and/orcooling capabilities (e.g., cooling coils) and temperature measurementinstrumentation. Pressure in the vessel may be monitored using suitablepressure measurement instrumentation, and the level of reactants in thevessel may be controlled using a level regulator (not shown), employingtechniques that are known to those of skill in the art. The contents maybe stirred continuously or semi-continuously with a mechanical mixingapparatus, for example. Vessel 10 may be operated at room temperatureand atmospheric pressure. As mentioned above, sodium hydroxide or otheralkali may be introduced via inlet line 14 for raising the pH when thepH of the feedwater in line 25 is below a desired value.

Product gas and unconsumed chlorine gas may exit vessel 10 via gas line17. Unreacted treatment gas may be removed from line 17 and recycled toHSD 40 or vessel 10, if desired. The temperature and pressure of highshear system 1 vary depending on the feedstream, the type of oxidantemployed, and the mixing attained in high shear device 40. Reactor 10may be operated under pressure. Conditions of temperature, pressure,space velocity and chlorine gas ratio which are similar to those used inconventional water treatment may be employed. By way of example, thechemical oxidation may be operated at a pressure in the range of fromabout 200 kPa (30 psig) to about 310 kPa (45 psig). In embodiments,chemical oxidation occurs at a pressure of about 240 kPa (35 psig). Inembodiments, oxidation is carried out at or near room temperature.

In the embodiment of FIG. 1, product exits vessel 10 by way of line 16.In embodiments, product stream in line 16 comprises water and solids.Product in line 16 may be introduced into separator 30. Treated water isseparated from solids in separator 30. In embodiments, the solids areflocculated and float as a sludge layer above the water and treatedwater is removed from the bottom portion of separator 30. In suchembodiments, line 35 may introduce a flocculating agent into line 16 toenhance the flotation of the solids above the treated water and theseparation in separator 30. In other embodiments, product in line 16 isintroduced into separator 30, the solids are allowed to settle to thebottom of separator 30, and treated water is removed via a line 33 fromthe top portion of separator 30. In embodiments, the treated water isfurther processed, for example the pH of the treated water may beadjusted. A portion of the treated water may be recycled to HSD 40 via,for example, line 45. Such recycle of treated water may be used toadjust the pH of the water in line 21. Solids separated from the treatedwater as sludge in separator 30 may be sent for disposal.

The resulting treated solid waste material separated from treated waterin separator 30 may be at least about 99% disinfected, alternatively99.9%. The production of offensive odors may be minimized and/or thesludge separated from the treated water may be sufficiently disinfectedor stabilized that it may be used as fertilizer material or may beapplied as ground cover. The high shear water treatment system andmethod may produce a sludge which is equivalent to what is called a“process to further reduce pathogens” (referred to as PFRP) in whichsubstantially all of the bacteria and pathogens within the material aredestroyed.

Multiple Pass Operation. In the embodiment shown in FIG. 1, the systemis configured for single pass operation, wherein the output 16 fromvessel 10 goes directly to further processing for recovery of treatedwater. In some embodiments it may be desirable to pass the contents ofvessel 10, or a liquid fraction thereof, through HSD 40 during a secondpass. In this case, line 16, line 33, or line 36 may be connected toline 21 for example via line 45, such that at least a portion of thecontents of the line is recycled from vessel 10 or separator 30 andpumped by pump 5 into line 13 and thence into HSD 40. Additionaltreatment gas may be injected via line 22 into line 13, or it may beadded directly into the high shear device (not shown).

Multiple High Shear Mixing Devices. In some embodiments, two or morehigh shear devices like HSD 40, or configured differently, are alignedin series, and are used to further enhance water treatment. Theoperation of multiple HSDs may be in either batch or continuous mode. Insome instances in which a single pass or “once through” process isdesired, the use of multiple high shear devices in series may also beadvantageous. In some embodiments where multiple high shear devices areoperated in series, vessel 10 may be omitted. For example, inembodiments, outlet dispersion in line 18 may be fed into a second highshear device and subsequently into any number of additional high sheardevices or into separator 30 or an aeration pond or lagoon. Whenmultiple high shear devices 40 are operated in series, additionaltreatment gas may be injected into the inlet feedstream of each device.In some embodiments, multiple high shear devices 40 are operated inparallel, and the outlet dispersions therefrom are introduced into oneor more vessels 10. In other embodiments, multiple high shear devices 40are operated in parallel and the outlet dispersions therefrom areintroduced into one or more separators 30, aeration ponds or lagoons.

Features. Without wishing to be limited to a particular theory, it isbelieved that the level or degree of high shear mixing is sufficient toincrease rates of mass transfer and also produces localized non-idealconditions that enable reaction/interaction to occur that may nototherwise be expected to occur based on Gibbs free energy predictions.Localized non ideal conditions are believed to occur within the highshear device resulting in increased temperatures and pressures with themost significant increase believed to be in localized pressures. Theincrease in pressures and temperatures within the high shear device areinstantaneous and localized and quickly revert back to bulk or averagesystem conditions once exiting the high shear device. In some cases, thehigh shear mixing device induces cavitation of sufficient intensity todissociate one or more of the reactants into free radicals, which mayintensify a chemical reaction/interaction or permit a reaction to takeplace at less stringent conditions than might otherwise be required.Cavitation may also increase rates of transport processes by producinglocal turbulence and liquid micro-circulation (acoustic streaming). Anoverview of the application of cavitation phenomenon inchemical/physical processing applications is provided by Gogate et al.,“Cavitation: A technology on the horizon,” Current Science 91 (No. 1):35-46 (2006). The high shear mixing device of certain embodiments of thepresent system and methods induces cavitation whereby treatment aid andcontaminant are dissociated into free radicals, which then interact.

The present methods and systems for water treatment incorporate anexternal high shear mechanical device for providing rapid contact andmixing of chemical ingredients in a controlled environment in thereactor/high shear device. The high shear device reduces the masstransfer limitations on the reaction/interaction and thus increases theoverall reaction/interaction rate, and may allow substantial reactionunder global operating conditions under which substantial reaction maynot be expected to occur.

In embodiments, use of the disclosed process comprising mixing viaexternal high shear device 40 allows an increase in production (greaterthroughput) from a process operated without high shear device 40. Inembodiments, consumption of treatment gas (e.g., chlorine, oxygen orair) and/or liquid flocculant is reduced when compared to watertreatment in the absence of external high shear device 40.

In embodiments, the method and system of this disclosure permit designof a smaller and/or less capital intensive process allowing selection ofa reactor 10 (and/or tank 30) having reduced volume than previouslypossible without the incorporation of external high shear device 40. Inembodiments, the disclosed method reduces operating costs/increasesproduction from an existing process. Alternatively, the disclosed methodmay reduce capital costs for the design of new processes.

Potential benefits of the high shear system include, but are not limitedto, faster cycle times, increased throughput, reduced operating costsand/or reduced capital expense due to the possibility of designingsmaller vessels. In embodiments, the process of the present disclosureprovides for a higher level of contaminant removal during watertreatment than conventional water treatment processes comprising anabsence of external high shear mixing. In embodiments, the degree ofmixing in external high shear device 40 is varied to attain a desireddegree of removal of a specific contaminant. In embodiments, the highshear water treatment process of the present disclosure reducestreatment gas (e.g., chlorine, oxygen, air) usage. In embodiments, theuse of the present system and method for the water treatment makeseconomically feasible the use of reduced amounts of chlorine, byincreasing the rate of contaminant oxidation, etc.

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, and so forth). Use ofthe term “optionally” with respect to any element of a claim is intendedto mean that the subject element is required, or alternatively, is notrequired. Both alternatives are intended to be within the scope of theclaim. Use of broader terms such as comprises, includes, having, etc.should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,and the like.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the preferred embodiments of the present invention.The disclosures of all patents, patent applications, and publicationscited herein are hereby incorporated by reference, to the extent theyprovide exemplary, procedural or other details supplementary to thoseset forth herein.

1. A method for removing contaminants from feedwater, the methodcomprising: combining the feedwater and a treatment gas and subjectingthe combination to at least two stages of high shear to produce a highshear treated product, wherein the treatment gas is a gas selected fromthe group consisting of air, oxygen, chlorine, and combinations thereofand wherein each stage of high shear subjects said combination to ashear rate of at least 20,000 s⁻¹.
 2. The method of claim 1 wherein thefeedwater is selected from the group consisting of waste water, surfacewater, groundwater, and combinations thereof.
 3. The method of claim 1wherein the contaminant is selected from the group consisting ofhydrogen sulfide, hydrocarbons, particulate matter, bacteria, andvolatile components.
 4. The method of claim 1 wherein subjecting thecombination to high shear produces a dispersion comprising gas bubbleshaving a mean diameter of less than 5 μm.
 5. The method of claim 4wherein subjecting the combination to high shear produces a dispersioncomprising gas bubbles having a mean diameter of less than 1 μm.
 6. Themethod of claim 5 wherein the gas bubbles have a mean diameter of nomore than 400 nm.
 7. The method of claim 1 wherein at least one of theat least two stages of high shear subjects the combination to a shearrate of greater than about 40,000 s⁻¹.
 8. The method of claim 1 whereinsubjecting the combination to at least two stages of high shearcomprises introducing the combination into a high shear device, whereinthe high shear device comprises at least two generators, each generatorcomprising a rotor and a complementarily-shaped stator, and wherein atleast one rotor is rotated at a tip speed of at least 22.9 m/s (4,500ft/min).
 9. The method of claim 8 wherein the high shear device producesa local pressure of at least about 1034.2 MPa (150,000 psi) at the tipof at least one rotor during operation.
 10. The method of claim 8wherein the energy expenditure of the high shear device during operationis greater than about 1000 W/m³ of fluid.
 11. The method of claim 8wherein the high shear device comprises a colloid mill.
 12. The methodof claim 8 wherein subjecting the combination to at least two stages ofhigh shear to produce a high shear treated product comprises passing thecombination radially outward over the rotor of the first generator anddownward to the second generator.
 13. The method of claim 1 furthercomprising: introducing the high shear treated product into a vessel;and extracting particle-containing water from the vessel.
 14. The methodof claim 13 further comprising introducing at least a portion of theparticle-containing water into a separator and extractingparticle-reduced water from the separator.
 15. The method of claim 14wherein subjecting the combination to at least two stages of high shearcomprises introducing the combination into a high shear device, andfurther comprising recycling at least a portion of theparticle-containing water, at least a portion of the particle-reducedwater, or both, to the high shear device.
 16. The method of claim 13further comprising removing a gas from the high shear treated product.17. The method of claim 1 further comprising: introducing the high sheartreated product into a vessel from which an aqueous product is removed;and separating particles from the aqueous product.
 18. The method ofclaim 17 wherein the contaminants comprise dissolved organic matter,wherein the treatment gas comprises air or oxygen, wherein the vessel isan aeration vessel comprising micro-organisms that consume organicmatter, and wherein the particles separated from the aqueous productcomprise micro-organisms.
 19. The method of claim 18 further comprisingrecycling at least a portion of the micro-organisms to the aerationvessel.